Electrode for neon signs



Nov. 1, 1932. J. J. MADlNE ELECTRODE FOR NEON SIGNS Filed Feb. 9. 1927 I (KP/Toy,

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Patented Nov. 1, 1932 JOHN J. IADINE, 01' I108 ANGEL ES, CALIFORNIA ELECTRODE I03 NEON SIGNS Application filed February 9, 1927. Serial No. 188,857.

This invention relates to neon tubes which have come into general use for luminous signs.

In the ordinary neon tube the electrodes are placed in the end of the glass tube which is filled with neon gas. The wires of an electric circuit are connected to the electrodes, and they must extend through the ends of the tube. Much care must be exercised to'prom vide an absolute seal at the points where the l:res 1pyass through the tube so that it will not lea My invention concerns a novel design of electrode which is placed at the end of the glass tube in such a manner that a wire can be connected directly thereto, not passing through the wall of the glass tube.

It is an object of my invention to provide an electrode which is mounted entirely on the an exterior of the glass tube.

It is a further object of my invention to provide a method of mounting the electrode on the glass tube.

Other objects and advantages of the invention will be made evident hereinafter.

Referring to the drawing in which I illus trate my invention:

Fig. 1 is a view of a neon gas sign utilizing the invention.

Fig. 2 is a view showing fragments of a tube having electrodes of my invention attached thereto.

Figs. 3, 4 and 5 are fragmentary sectional views illustrating the steps constituting the process of this invention.

Referring to the drawing and particularly to Fig. 1, 11 represents a sign having a plate 12 in which channels 13 are formed. Resting in the channels 13 is a neon tube 15 which is formed so as to spell a word. The opposite ends of the tube 15 are provided with electrodes 16 to which conductors are connected.

Portions of the neon tube 15 which are not to mounting it on the tube 15 will be described. As shown best in Fig. 3 the electrode 16 of the invention is cup-shaped and is preferably made of copper or of a com osition of metals,

of. which copper is used in arge proportions.

The electrode 16 has a cylindrical wall. 20 and an end wall 21, from which end wall 21 an attachment lug 22 is extended. Projecting from the open end of the cylindrical wall 20 is a cylindrical lip 23 which is much thinner than the cylindrical wall 20. The lip 23 is formed by turning down or spinning the open end of the cylindrical wall 20. When the electrode is mounted on the tube 15, as shown in Figs. 2 and 5, the end of the cylindrical lip. 23 surrounds the end of the glass tube 15 and is partly fused to it.-so that an absolute air-tight-seal is formed. A conductor, as indicated by the numeral 25 in Fig. 2, is

attached to the attachment lug 22. The fea- "q ture of of the electrode is that it is located entlrely on the exterior of the glass tube 15.-

The conductor 25 may be attached directly to the electrode and does not have to be extended through a wall of the glass tube 15. This is a very important accomplishment because ofthe fact that it is very diflicult to form a tight and permanent seal around a conductor which is extended through the wall ofthe glass tube, as is necessary when theordi- 30 nary electrode is employed.

In installing the electrode 16, the process is conducted as follows: In Fig. 3 the electrode and one end of the glass tube 15 are shown in their natural shapes at the commencement'of the process. The first step is to heat an end 27 of the glass tube 15, preferably raising it to a fusing temperature. This causes the end of the tube to expand as illustrated in Fig. 4. It may also be desirable to v slightly heat the cylindrical lip 23 so that it will expand into a position indicated by the numeral 28 in Fig. 4. The lip, as shown at 28, then provides a cylindrical opening which is just large enough to receive the end n.7, 27, the end 27 being moved so as to extend within the lip 23 as indicated by dotted lines 29 of Fig. 4. The coefiicient of expansion of glass is from .033 to .045, whereas the coefficient of expansion of copper is from .092

to .104. It will be seen, therefore, that it takes much less heat to expand the cylindrical lip 23 to receive the end 27 than it doesto raise the end 27 to a fusing temperature.

When the end 27 of the glass tube 15 comes in contact with the cylindrical lip 23, the cylindrical lip is imme iately raised to a very high temperature and fusion between the 11p and the'end of the glass tube takes place.

en the parts are cooled, they occupy the shape shown in Fig. 5. It will be seen that the outer diameter\of the glass tube 15 is larger than the inner diameter of the cylindrical lip 23 before the method was commenced; therefore, larger than it was at first. In view of the fact that the thickness of the wall of the lip 23 is quite small, the metal may readily stretch so that it will surround the end of the tube 15 without rupturing.

The method of assembling the electrode and the tube is very important to the invention since it makes it possible to install the electrode so that there can be no leakage. The stretchin of the end of the lip 23 and the fusing o the lip-23 to the end of the glass tube 15 assure an absolutely tight seal.

Certain definite and important advantages result from the electrode described, especially when used in connection with any of the gases of thenoble monatomic group, of which neon is an example. Such gases, it has been found, are rapidly occluded if no precautions be taken, so that the life of the tube is usually very short. It is found that when the form ofelectrode as described is used. a long tube life, without gas replenishment, is ensured.

The occlusion of the gases in the tube is due to the heat of the electrode surface, which induces sputtering. With ordinary internal electrodes, it is impossible to reduce the electrode temperature; therefore expedients have been suggested to maintain the electrode dro low, as y increasing the active electrode surface to a very large degree. This expedient is unnecessary with the external type of electrode. The electrode 16 has a large external surface, open to the atmosphere. This rovides' a large and effective radiating su ace, and the body of the electrode is kept cool. No material sputtering is noticed; and the tubes having comparatively small external electrodes have been found to have active lives of the order of thousands of hours.

This phenomenon, it is believed, is due directly to the good heat radiation provided for the electrode 16. The metal of the electrode is exposed to such. an extent that heat transfer to the surrounding air is rapid; and the active electrode surface never gets hot enough to cause material trouble.

The only instance of which I am aware in which a successful attempt has been made to hold down the temperature of the electhe end of the lip 23 is p longer life for the tube than is,

trode is shown in patent to Claude 1,125,47 6, January 19, 1915. In this patented structure, to decrease the vaporization of the electrodes and prevent the consequent forma tion upon the walls of the tube, in proximity to said electrodes, of deposits containing the neon gas, whereby the luminosity of the tube is maintained constant for a considerable period of time' without fresh introduction of gas, the electrode is enclosed entirely within the end of the lass tube and has to be made so large (i. e., aving an area exceeding 1.5 square decimeter perampere of current) that the tube has to be greatly enlarged to form a cumbersome bulb at the end thereof. The formation of this elongated bulb at each end of the tube renders this Claude device expensive to manufacture and handle. In actual practice, a large percentage of the cost of using these signs is caused by breakage of the tubes, the end-bulbs being comparatively heavy and therefore easily broken off in course of manufacture and handling and shipping and even while in use All these disadvantages are obviously done away with by my construction. As a matter of fact, my construction is so-easily made, handled and utilized in building a sign that I can readily and economically use my electrodes for single letters, whereas with the Claude device the bulbs are so large and expensive that it is out of the question to use the Claude device anywhere except at each end of the sign, a single tube bein used for all the letters, as is well known. y device, therefore, can be made, installed and used at a greatly reduced cost as compared with the Claude tube, now in general use. I have found also in actual practice that by usin an electrode of the type I claim (by whic I can get practically more external surface for radiation of heat to the atmosphere then I provide for active contact with the gas in the tube), I obtain a much to my knowledge, ossible with an electrode of the Claude type, y reason of the fact that my electrode stays cool, thus almost entirel preventing occlusion by the walls of the tu thus keeping the gas in the tube at full pressure. It will be 0 served that radiation is promoted by having the exterior heat-radiating surface of the electrode greater than the active interior surface of the electrode.

'I claim as my invention 1) 1. A high voltage luminous discharge tube having a filling ofgaseous product of the noble monatomic group, and an electrode structure sealing the tube for conducting current to the column of gas in the tube, said structure includin a hollow member having an internal 0 lindi'ical surface forming the main active-e ectrode area, the external area of the member being exposed and providing a connection means to a source.

2. A high voltage luminous discharge tube I having a filling of gaseous roduct of the noble monatomic group, an an electrode structure sealing the tube for conducting current to the column of gas in the tube, said 'I structure including a hollow member having an internal cylindrical surface formingrthe main active electrode area, the external area of the member being exposed and providing a connection means to a source, the said internal area formin virtually an extension of the internal area 0 the tube.

3. A high voltage luminescent tube containingrare gas of the atmosphere, comprising a glass tube open at its opposite ends, and

II a thimble electrode telescoped with respect to the open end and sealing it, at least a part of the internal cylindrical area of the thimble being in direct contact with the gas to form the main electrode area, and the exter- 20 nal area of the thimble being exposed to the atmosphere and providing a connection means to a source.

f 4. A high voltage luminous discharge tube having a filling of gaseous product of the no- 35 ble monato'mic group, and an electrode structure sealing the tube, said structure including a hollow member having an internal cylindrical surface forming the main active electrode area, and also having an external sur- 30 face on the opposite side of the wall of the hollow member, exposed to the atmosphere andarranged to be in detachable connection with a source. to

In testimony whereof, I have hereunto set 35 my hand at Los Angeles, California, this 31st day of January, 1927.

JOHN J. MADINE. 

